This discussion makes me believe RR needs to be listed numerically on each tire pulled at its rated weight and inflation pressure.

I thought RR ratings were law

What happen

US regulations were first published in the 2010 timeframe, but were withdrawn for technical reasons. The latest is that new regulations are supposed to be published June 2019.

If you want more detail about what the technical problems were that caused the first set of regulations to be withdrawn, say so and I'll explain. Warning: It will be a bit long as the issues are complex.

There were 3 issues that needed to be resolved if a regulation was to be put in place:

1) What test to perform. There are several different tests, but it turns out that tires can be compared using a single point test – quick and easy.

2) How to correlate different testing facilities. They decided on assigning a value to the SRTT (Standard Reference Test Tire), then adjusting the results based on those values. The SRTT is a commonly used reference where tests can vary by – say – temperature or testing surface. It’s an old Uniroyal tire that Michelin makes using certified materials and they test to assure the tire hasn’t changed from batch to batch (and if it has, how to adjust the results.)

3) How to express the result so that it is easy for the average consumer to understand. This is where the technical issues got in the way.

First, rolling resistance varies by tire size. So a way needed to be developed to deal with that. NHTSA (National Highway Traffic and Safety Administration) wanted EVERY size to be tested in EVERY tire line for EVERY tire manufacturer. USTMA (US Tire Manufacturers Association) pointed out that it would take 3 years of 24/7 testing to achieve that result – and during those 3 years no research could be done – and that just wasn’t going to fly.

Second, NHTSA wanted to use RRF (Rolling Resistance – Force) in order to push consumers to buy smaller cars. The USTMA pointed out that consumers wouldn’t buy cars based on the tire’s rolling resistance even if they had that information. They would use the fuel economy values published by the vehicle manufacturers – AND that consumers would be better served if RRC (Rolling Resistance Coefficient = RRF divided by the test load) was what was published.

Then there was the issue of how to display this information – which kind of got lost in the 2 points above. One proposal was a traffic light (Red/Yellow/Green) kind of indicator without the actual values being published. Another was a bar graph showing where a particular tire was compared to the best and worst tire – but that meant that any new max or min values would result in obsoleting the previous published graphs.

In the end the proposed rule was withdrawn to work out the 2 issues mentioned above – the size issue and the RRF vs RRC. This was in 2010. In the meantime, there was this HUGE airbag recall that occupied most of the technical resources of NHTSA, so the Rolling Resistance regulations weren’t worked on – until recently.

The publication date has been pushed back repeatedly – and I expect it to be pushed back some more based on the current administration's attitude towards regulations.